Various synthetic methods for producing a water-soluble conductive polymer having an acidic group such as a sulfonic acid group or a carboxyl group have been investigated since the water-soluble conductive polymer exhibits excellent solubility in water or an organic solvent by the hydrophilic action of its acidic group. For example, self-doping acidic group-substituted polyaniline which can exert conductivity without the addition of a doping agent thereto has been proposed. As a synthetic method thereof, a method for polymerizing an acid group-substituted aniline such as a sulfonic acid group-substituted aniline or a carboxyl group-substituted aniline by using an oxidizing agent in the presence of a basic reaction auxiliary has been proposed.
In addition, a great number of conductors including a conductive polymer film such as an antistatic film containing a water-soluble conductive polymer having an acidic group as a main component or production methods thereof have been reported (for example, see Patent Literature 1).
However, a water-soluble conductive polymer having an acidic group exhibits solubility in water, and thus a conductive polymer film such as an antistatic film formed from this exhibits insufficient water resistance. Hence, a conductor including an antistatic film is not suitable for an application requiring water resistance so that there is a restriction on the application thereof. For the purpose of imparting water resistance to an antistatic film, although a method for blending a high molecular compound with a water-soluble conductive polymer having an acidic group has also been proposed, the desired water resistance is not necessarily satisfied.
As a method for solving the problem related to water resistance, a conductive composition containing a water-soluble conductive polymer having a sulfonic acid group and/or a carboxylic acid group and a compound (hereinafter, referred to as the crosslinking compound in some cases) having at least two functional groups which can react with the sulfonic acid group and/or the carboxylic acid group in the water-soluble conductive polymer has been proposed (for example, see Patent Literature 2). According to this conductive composition, it is possible to form a conductor exhibiting water resistance and acetone resistance by heating a composition to which a crosslinking compound such as polyvinyl alcohol is added at 100° C. or higher.
In addition, a method for insolubilizing a water-soluble conductive polymer having a sulfonic acid group and/or a carboxylic acid group by heating it at a high temperature of 150° C. or higher has been proposed (for example, see Patent Literature 3).
In addition, a conductive composition containing a thickener, an organic solvent to dissolve or disperse a water-soluble conductive polymer, and water in addition to the water-soluble conductive polymer having a sulfonic acid group and/or a carboxylic acid group and a compound having at least two functional groups which can react with the sulfonic acid group and/or the carboxylic acid group in the water-soluble conductive polymer has been proposed (for example, see Patent Literature 4). According to this conductive composition, sagging on the substrate hardly occurs and a conductive composition layer exhibiting excellent drying property can be formed. Furthermore, a conductor in which cissing on the substrate is prevented can be formed as the coating property of the conductive composition to a substrate is improved by blending a surfactant.